mvssysprog

Thank you for your comments. I had a fast-read thermometer attached to the register in my office last summer and in the afternoon, the temperature of the air coming into my office was initially at 136 degrees for the first few seconds. It took over a minute for the air to drop below a 100 degrees. One of the first things I checked when i moved into my house was to make sure that the soffit vents were unobstructed by insulation (and they weren't). We have a ridge vent, so I would have thought that we would have had proper ventilation. One of the complicating factors in the heat accumulation is that we have a very steep roofline facing south. I readily concede that we are not as hot as other parts of the south. All I am trying to do with the foam is to lower the temperature differential between the attic and the rest of the house. Thanks.....Dave

Thank you for commenting. Your point is well taken. When we were building the house, I contracted with an engineering firm to size the heat pump system that was installed. So I am reasonably certain that it is sized properly for the size home we have. My intention was not to condition the space for use. Rather, to eliminate the extremes in temperature we have experienced coming out of our ductwork for the first minute or two until the heatpump has a chance to do its work.

I live in Bluffton, SC and it get extremely hot in the attic during the summer (it hit 152 on my min/max thermometer last summer). Our air handlers are in the attic, so needless to say we get significant blasts of hot air coming out of the ductwork during the summer, and very cold air coming out in the winter. There is 10 inches of insulation on the attic floor but no insulation anywhere else (ductwork is flexible - r6). I have been looking at installing foam insulation to condition the attic so that I don't get the extreme temperatures coming through the ductwork. I have talked to a number of foam insulation installers in the area and can't seem to get a straight answer as to which way to go; open-cell or closed-cell. It gets extremely humid here during the summer. If we use closed-cell, where does the humidity in the attic already there go? Several of the contractors suggested using closed-cell because of the better r-rating. I also spoke to someone who pointed out that in the mornings when the roof tiles are moist from the nightly dew, vapor pressure from the sun on the moisture could push the moisture through the paper and roof into the attic. If we used closed-cell, where would the moisture go except against the roof. Could this cause the plywood to rot over time? If we used closed-cell, and sealed the ridge vent, how would the attic breathe? If we use open-cell is there a greater risk of mold and mildew during the summer months? I know it's a lot of questions, but I can't seem to get a straight answer from the contractors I have spoken to. Any help would be gratefully appreciated... Dave